DNA evidence points to humans for demise of moas

DNA says we are guilty. Early human settlers probably did wipe out the moas of New Zealand. Moa DNA suggests that their population was stable before we turned up.

New Zealand was home to nine species of flightless moa until humans arrived around AD 1300. Within a century, they were all gone. The archaeological record shows humans hunted moas, perhaps to extinction.

Morten Allentoft of the University of Copenhagen, Denmark, and colleagues studied DNA from 281 fossils of four moa species. They found that moa genetic diversity was nearly constant for 3000 years before their extinction, a sign of a stable population. "We can only blame ourselves," says Allentoft.

No long fuse

Allentoft's findings contradict earlier studies by Neil Gemmell at the University of Otago in Mosgiel, New Zealand. In 2004 he studied mitochondrial DNA from moa fossils and found that New Zealand had a moa population of 3 to 12 million between 4000 BC and AD 1000. A separate study had said there were just 159,000 moas when the first humans arrived 300 years later, so Gemmell suggested that something else had depleted moa populations before human hunting.

But those estimates aren't reliable, as DNA isn't a good record of population size, says Allentoft. It is only good for showing trends.

The new study "appears to take care of the 'long fuse' decline in moa species", says Ross MacPhee of the American Museum of Natural History in New York, who wasn't involved in either study.

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